Plastic bags are extensively used to package goods. Plastic bags are typically manufactured from a tube of blown plastic film. The tube of plastic film can be folded inward on the sides to form 4-layer gussets. The middle of each bag has only 2-layers of plastic film. Tubes can be cut to a predetermined length, and an electric-heating iron may be used to seal (or weld) a bottom edge of the tube to form the bag body. Plastic bags manufactured using this method may be of various configurations, including flat-mouth bags with or without carrying straps, and vest-style bags with carrying straps. Vest bags are so named because they resemble a garment that is worn on the upper body of a person. Plastic bags of this structure can facilitate storage and carrying of various types of goods. However, they have poor load-bearing capacity. The reason is that the 4-layer gusseted sides of the plastic bag are directly hot-sealed to the intermediate 2-layer film near a bottom edge of the bag. The intersection of 4-layer film and 2-layer film becomes a stress concentration and a point of frequent failure. Breakage at the bottom affects the load-bearing capacity of the plastic bags and may also lead to leakage.